(1) Field of the Invention
The invention relates to a centrifugal pump impeller having pump blades made of a plastic material processed by injection molding technology for an electromotive centrifugal pump consisting of a base body having a bearing to which is attached, at one end, a permanent-magnetic rotor and, at the other end, a cover disk that is mounted on the base body.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Centrifugal pumps are frequently used as auxiliary water pumps in motor vehicles and mostly assist belt-driven main cooling water pumps. Thanks to their superb controllability, centrifugal pumps are generally also integrated into brushless DC motors. These motors possess a wound stator and a permanent-magnetic rotor that form a compact assembly with a centrifugal pump impeller. The rotors can be configured both as internal rotors and as external rotors. The centrifugal pump impeller is located in a wet chamber, which is sealed off by a partition wall from a dry chamber that includes the stator. Centrifugal pump impellers generally consist of a permanent-magnetic area and a hydraulic area. The hydraulic area comprises a disk and pump blades attached to it that project the pumping medium radially outward, thereby generating a pump pressure. Open centrifugal pump impellers and closed ones that have a cover disk are known. Centrifugal pump impellers with cover disks are more efficient but are more difficult to manufacture. In the case of centrifugal pump impellers manufactured using injection molding technology, especially problematic is the demolding process of the relatively complicated mold. That is why the cover disks are often manufactured separately and then installed.
A generic centrifugal pump impeller with a cover disk is known from WO 2011/131251 A1. It consists of plastic material processed by injection molding technology, the base body forming one piece with the permanent-magnetic rotor and consisting throughout of a plastic-bonded magnet material. The impellers form one piece with the cover disk and consist of a plastic material without permanent-magnetic components. The separation into two parts enables the mechanical and permanent-magnetic properties of the function to be correspondingly optimized. However, since the base body also contains permanent-magnetic material, the cost of materials is higher. This is especially true when higher-quality permanent-magnetic materials are used. In the known centrifugal pump impeller, the pump blades always have a width that corresponds to the distance from the base body up to the cover disk, so that there is no gap between them. However, studies have shown that from a flow technology point of view, it is more desirable if the pump blades have a lead-in chamfer on the inside. However, in the case of the known pumps, for manufacturing technology reasons this cannot be realized or can be realized only at great expense.
Therefore, the problem solved by the present invention is to ensure that a centrifugal pump rotor of the kind mentioned at the outset has a simple design, is more efficient and can be manufactured economically.